1. Field
The present disclosure relates to a synergistic herbicidal composition containing mesotrione and thifensulfuron-methyl, each in particular crystal modifications. The composition finds use in controlling the growth of undesirable plant, particularly in crops, including using the aforementioned composition.
2. Description of Related Art
The protection of crops from undesirable plant, which inhibits crop growth, is a constantly recurring problem in agriculture. To solve this problem, researchers are trying to produce an extensive variety of chemicals and chemical formulations effective in the control of such undesirable growth. Chemical herbicides of many types have been disclosed in the literature and a large number are in commercial use.
Some herbicidal active ingredients have been shown to be more effective when applied in combination rather than applied individually, this effect being referred to as “synergism.” According to Herbicide Handbook of the Weed Science Society of America, Seventh Edition, 1994, page 318, “synergism” is an interaction of two or more factors such that the effect when combined is greater than the predicted effect based on the response to each factor applied separately.
The compound 2-(4-mesyl-2-nitrobenzoyl)cyclohexane-1,3-dione has the common name “mesotrione”. Mesotrione is a substance that can form polymorph crystals. Two different forms, crystalline modifications I and II, of mesotrione are described in WO2006021743, which is incorporated herein by reference for all purposes. Mesotrione is active as a herbicide and is now commercially available in a range of formulations for controlling the growth of undesirable plant. The XRD diffraction data for mesotrione crystal form I from the above publication are given below, although some peak shifting may be possible.
Peak Position (2-Theta)Peak Position (d spacing)8.5210.3417.085.1817.435.0818.744.7319.044.6619.314.5919.524.5421.154.2025.733.4628.663.11
The compound methyl 3-(4-methoxy-6-methyl-1,3,5-triazin-2-ylcarbamoylsulfamoyl)thiophene-2-carboxylate, having the common name “thifensulfuron-methyl”, is a member of the sulfonylurea group of chemicals and used as herbicide. Thifensulfuron-methyl is a selective post-emergence sulfonylurea herbicide for the control of broadleaved weeds in cereals and soybeans. Like other sulfonylureas, the mode of action is via inhibition of the enzyme acetolactate synthase (ALS), and thus prevention of the biosynthesis of the essential amino acids isoleucine and valine.
The commercially available thifensulfuron-methyl, which is usually manufactured by the process described in U.S. Pat. No. 4,481,029, which is incorporated herein by reference, where it is present in an amorphous state.
It has been found that thifensulfuron-methyl in the amorphous state is highly viscous, which is not suitable for being prepared as compositions or formulations having spray equipment cleanout property. Thifensulfuron-methyl residues remain in the spray equipment after spraying. Adequate cleanout prior to reuse of the spray equipment will typically require a rinsing procedure that is not only time-consuming but also results in wastewater disposal problem.